Knockdown shelving assemblies are available in many forms. One form includes knockdown shelving assemblies such as those disclosed in LaKaff U.S. Pat. No. 3,182,846 and Kelson U.S. Pat. No. 3,344,756 wherein shelves are fixed to shelf supporting standards using set screws or other such threaded fasteneing means.
The knockdown shelving assembly disclosed by LaKaff includes a shelf having an object supporting central planar portion. An engaging element is affixed to the shelf and has a conical wall defining a frusto-conical cavity with the conical wall being sloped with respect to a line perpendicular to the shelf central planar portion and diverging outwardly away from the central planar portion of the shelf. A frusto-conical male element on the end of a shelf supporting standard is received in the engaging element cavity and the shelf supporting standard is rigidly attached to the shelf mounted engaging element by means of a threaded fastener.
A cabinet formed using a LaKaff type assembly can support heavy items on the shelves without adversely affecting the knockdown feature of the cabinet. However, a LaKaff type cabinet has shelf spacing which can only be an increment of supporting standard length. There can be no intermediate shelves between shelves located at the ends of the supporting standards, and thus, shelf designs using knockdown assemblies similar to the LaKaff assembly have only a limited number of set-up designs and configurations available. Furthermore, should one of a set of supporting standards become damaged or lost, the usefulness of the remaining supporting standards is adversely affected. In a worst case, an entire shelf level may have to be omitted simply because one standard of the set of standards cannot be used.
The problems associated with incremental shelf spacing are overcome by knockdown shelving assemblies such as that disclosed by Kelson which have shelves capable of infinite adjustment along the length of a supporting standard. The Kelson knockdown shelving assembly has a cylindrical shelf supporting standard attached to individual shelves by set screws engaging the longitudinally extending wear surface of the shelf supporting standard. The supporting standards of this assembly are received through holes defined in the shelves so the shelves can be moved longitudinally along the supporting standards. A shelf can be affixed to a supporting standard at any location on that standard by means of the set screws.
While a knockdown shelving assembly similar to the Kelson assembly has shelves which are infinitely adjustable, there is a danger that the shelves will move relative to the supporting standards if very heavy items are placed on the shelves, for the shelves are held in place only by the set screws abutting the longitudinally extending surfaces of the supporting standards. The weight supported on the shelves is directed axially of the supporting standards; whereas, the shelf-standard affixing force generated by the set screws is directed radially of the supporting standards. The shelves are thus supported only by the friction forces generated at the supporting standard cylindrical outer surfaces by the set screws.
Another form of knockdown shelving assembly includes knockdown assemblies similar to those assemblies disclosed in Maslow, U.S. Pat. Nos. 3,424,111 and 3,523,508 and Pollak, French Pat. No. 855,715, wherein shelves are affixed to shelf supporting standards by elements wedgingly forced together. Such knockdown shelving assemblies provide variety in shelf spacing greater than that variety provided by the incremental spacing of the Kelson type knockdown assemblies, and yet provide an engagement between a shelf and a supporting standard which is more secure than the engagement produced by elements included in LaKaff type knockdown shelving assemblies. The Maslow and Pollak knockdown shelving assemblies include a shelf having a central object supporting plane, and an engaging element is affixed to the shelf and has a conical wall defining a frusto-conical cavity with the conical wall sloping with respect to a line perpendicular to the shelf central object supporting plane and diverging outwardly away from the shelf central object supporting plane. The Maslow and Pollak knockdown shelving assemblies include a frusto-conical male sleeve element affixed to the longitudinally extending surface of a cylindrical shelf supporting standard, by a friction fit in the Pollak assembly and by engagement of ribs into indentations or notches on the supporting standards in the Maslow assembly. The sleeves can be moved on a shelf supporting standard in the longitudinal direction of that supporting standard, and the male frusto-conical sleeve element is received in the shelf-affixed frusto-conical cavity to attach the shelf to the supporting standard via a wedging engagement between the cavity defining conical wall on the shelf and the male frusto-conical sleeve element.
The frusto-conical male element is a split sleeve in the Maslow knockdown assembly and is an elastomeric element which is deformed and compressed into a frusto-conical shape by the wedging action between the frusto-conical cavity wall and the tubular support post in the Pollak knockdown assembly. The shelves of Pollak type knockdown assemblies are infinitely adjustable on the shelf supporting standards, but are subject to movement on the supporting standards if heavy objects are placed on the shelves, as the wedged elements of this assembly include an elastomeric element which has limited ability to withstand the shelf weight generated forces.
A Maslow type knockdown shelving assembly has a metal male sleeve element used as one of the wedging elements and thus is more stable and less susceptible to shelf movement on the supporting standards than is a Pollak type shelving assembly. The tightness of fit between the shelf and the supporting standard affixed frusto-conical sleeve element of Pollak and Maslow type knockdown shelving assemblies is increased as shelf supported weight is increased. This result is desirable to provide reliable and secure shelf positioning, but presents drawbacks when the shelving assembly is knocked down. The wedging interference between the shelf supporting standard affixed frusto-conical sleeve element and the shelf affixed conical wall may be greater than can be overcome by hand. This drawback is especially evident in the Maslow type knockdown assemblies due to the metal-to-metal interference fit established between the shelf and the sleeve element. Using equipment such as hammers to remove a shelf from a supporting standard is not at all desirable as the shelf or the supporting standard may be damaged by the hammer, and the force required for separating the shelf and the supporting standard may exceed the strength of the person knocking down the shelving assembly if no hammer is available.
Accordingly, there is need for a knockdown shelving assembly which will securely and reliably support heavy objects in a multiplicity of positions, yet which will permit a shelf to be easily disassembled from a shelf supporting standard.